Folding cellular telephones, which have prevailed in recent years, each comprise a first housing having a speaker and a display section (liquid crystal display), a second housing having a microphone and an operating section such as input keys, and a hinge section for rotatably connecting the first housing with the second housing. Such folding cellular telephone is folded when not being used so as to be portable or suitable for carrying around. In using the folding cellular telephone, a user rotates the first and/or second housings on the hinge section as the axis of rotation to unfolded (opened) positions so that he/she can operate the keys while viewing the display section or have a conversation by the telephone through the speaker and microphone.
Each of the housings has certain degree of weight since it is provided with a built-in electronic circuit board, a liquid crystal display (LCD), a battery and the like. Therefore, a spring or the like is incorporated in the hinge section as a supporting mechanism that makes the upper side housing flip up to help the user unfold the cellular telephone. The folding cellular telephone is also provided with a mechanism for preventing the telephone from being easily refolded. Besides, some folding cellular telephones have a mechanism by which the hinge supports the first and second housings for movement in the folding (closing) direction if the angle between the housings decreases on the occasion when the telephone is folded. As just described, the conventional folding cellular telephone adopts complicated open-close mechanisms so that the user can fold/unfold the telephone with only one hand when using the telephone.
In addition, more and more folding cellular telephones function as information terminals for sending/receiving e-mail messages, viewing Web sites on the Internet, playing games and the like as described in, for example, Japanese Patent Application laid open No. 2001-175609, Japanese Patent Application laid open No. 2001-358811 and Japanese Patent Application laid open No. 2002-176476. Accordingly, the size of the display section (LCD) tends to increase. Further, some folding cellular telephones are provided with a plurality of display sections. As an example, a small display is arranged on the back surface of the first housing for indicating simple information such as time, the telephone number of a calling party on receipt of a phone call, and the like so that the user can obtain the information even while the folding cellular telephone is folded.
In the case of using the original telephone functions of such folding cellular telephone that serves as an information terminal for sending/receiving e-mail messages, viewing Web sites on the Internet, playing games and the like, generally, the first and/or second housings are rotated to opened positions. Thereby, the user inputs the telephone number of the other party through the operating section such as input keys, and subsequently, checks the telephone number of the other party shown on the display, thus making a call to his/her party. After the connection is established, the user has a conversation with his/her party by the folding cellular telephone through the speaker and microphone placed on the edges of the respective housings. On this occasion, the folding cellular telephone consumes a measurable amount of electric power, if only temporarily, since the large display set on the inner surface of the housing displays information and also its backlight turns on.
There is disclosed a folding cellular telephone which is capable of serving the telephone functions regardless of whether or not it is folded in Japanese Patent Application laid open No. 2002-176476. The folding cellular telephone needs universal coupling joints for different rotation between its housings as a horizontal axis X for opening/closing movement and a vertical axis Y for front/back side-inverting movement, which run at right angles to one another. Consequently, the hinge section has a complex structure. Moreover, since part of information displayed on the large display set on the inner surface of the housing is viewed through a see-through window, the display requires more electric power.
Furthermore, input keys of the conventional folding cellular telephone are used for the information terminal functions such as for sending/receiving e-mail messages as well as the telephone functions. Therefore, in addition to numerals, alphabetic or other characters and the like are printed on the operation buttons or keys, and the user would have trouble seeing anything printed on the operation buttons when operating them.